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PPQS Flashcards

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1
Q

Suggest whteher clf3 HAS polar bonds

A

YES
- F more electronegative
- d+ cl, d- f

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2
Q

electronegativity

A

ability of an atom to attract the electronS in a covalent bond

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3
Q

why do repeats?

A
  1. increase repeatability
  2. find anomalies AND DISCARD
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4
Q

atomic emission spectra provisde evidence for …

A

quantum shells

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5
Q

6 MARKS
Problems and improvements of collection over water(gas collected 2 low)

A
  1. gas escapes from apparatus. use airtight bung with gas syringe
  2. metal covered with an oxide. clean with abrasive BEFORE weighing
  3. mass of metal used too low. use a more PRECISE balance
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6
Q

shortest bond length in CH3OH

A

O-H as largest difference in electronegativity

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7
Q

hydrogen bond angle

A

ALWAYS 180
- 2 bonding pairs
- 0 lone pairs

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8
Q

trigonal bipyrmaidal angles

A
  • 5 bp, 0 lp
  • 90 and 120
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9
Q

explain why the positive charge is on the carbon atom shown

A

tertairy carbocation is more stable than a primary carbocation
because it has more positive inductive alkyl groups

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10
Q

importance of termination (2)

A
  • 2 free radicals join together
  • dont form any free radicals
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11
Q

describe what is meant by cracking (2)

A
  • use of high temperatures
  • to break large molcules into smaller molecules, ,and produce alkenes
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12
Q

why can propene form 2 possible products with HBr

A
  • asymmetric alkene
  • Br could join to c1 or c2
  • to form 1 bromo or 2 bromo propane
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13
Q

biggest hazard of alkanes

A

flamable

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14
Q

in combustion where must the u-tube go

A

BEFORE boiling tube w lime water; distinguishes water as a product of combustion rather than the limewater

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15
Q

why can hydrogen chloride gas not conduct electricity but HCl acid can

A

covalent bond in hydrogen chloride changes to an ionic bond in aqueous solution

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16
Q

pressure in pvnrt is in

A

PASCALS

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17
Q

EXPLAIN WHY METHANOL IS SOLUBLE IN WATER

A
  • hydrogen bonding between them both
  • of same strength
  • comparable to the strength of the bonding in either component on its own
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18
Q

why is NaCL soluble in water but not methanol

A
  • hydration of BOTH ions in water
  • but ionic bonding is stronger than bonding between ions and methanol
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19
Q

2 reasons why x is more electronegative

A
  • more protons
  • smaller atomic radius
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20
Q

despit ehaving polar bonds why is x not polar

A
  • symmetricak
  • BOND POLARITIES CANCEL
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21
Q

use mexwell boltzmann diagram to explain why the use of a catalyst increases the rate of decomposition of ammonia (3)

A
  • area under curve represents fraction of molecules with E>= Ea
  • area with Ea of catalyst is greater; more molecules have E>= Ea
  • more freqeunt successful collision
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22
Q

similarities (2) and differences (2) between pi and sigma bonds

A

SIMILARITIES:
- both include the overlap of orbitals
- both involve electrostatic attraction between a BONDING pair of electrons and positive nuclei
DIFFERENCES:
- pi = sideways overlap of orbitals
- sigma = direct end on overlap of atomic orbitals

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23
Q

explain maxwell boltzmann at high temp

A
  • peak shifts to the right and lower
  • at higher temperatures there are more particles with higher energy
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24
Q

why might reaction not happen as shown

A
  • might react with oxygen
  • unlikely for reactants to be in correct ratio
  • reaction must occur in a series of steps as too many particles reacting in equation
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25
Q

+- of chemical test vs infrared to show alcohol

A

+
cheaper
rapid
can be done in schools
-
CHEMICAL TEST NOT AS SENSITIVE

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26
Q

vol gas a bit higher at higher temp

A

gases expand when heated

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27
Q

why is the measurement of initial rate less accurate than max

A
  • difficult to judge where tangent should be drawn for 0
  • compared to other points on the line
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28
Q

why is a heterogeneous catalyst good for gas reactant

A

provides a surface for the reaction

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29
Q

why might uncertainty of someone else be hgiher with mass measurement

A

they used a smaller mass w same balance

30
Q

why does catalyst not effect amount of product made

A

increases rate of forward and backward reactions

31
Q

why is catalyst heated and why might it melt

A
  • heated to provide activation energy
  • metls as bonds broken
32
Q

advatnage of catalyst iN INDUSTRY

A
  • decreases activation energy
  • allows milder conditions to be used (lowering cost)
33
Q

chromate (VI) ion colour

A

YELLOW

34
Q

WHY IS ice less dense than water

A
  • water molecules in a lattice
  • molecules further apart in ice than water
35
Q

TMS purpose

A

reference peak to compare other shifts to

36
Q

what does NMR actually do

A

change spin state of hydrogen nuckeus

37
Q

effect of increasing temp on rate constant

A

increases

38
Q

why is there at least 2 steps (RDS REFERENCE)

A
  • x and y in RDS (z not in)
  • but more reactants in full equation
  • so must be another step containing z
39
Q

why is the major product from the tertiary carbocation

A
  • most stable
  • inductive effect of alkyl groups
40
Q

why are the other reactant concnetrations in hUGE excess in iodine clock reaction

A
  • concentration remain constant
  • so that [I2] is limiting reagent; only its concnetration changes
    -OTHERWISE A CURVE IS OBTAINED AS FULL ORDER OF REACTION
41
Q

how to measure order of propanone as 1st order after already doing one step of iodine

A
  • doulbe conc of propanone
  • rate should double (gradient doubkes)
    OR
  • measure conc propanone over time
    -constant half life
42
Q

how to quench iodine TITRATION

A
  • add NAHCO3
  • neutralizes acid
43
Q

sodium hydrogencarbonate neutralising ACID catalyst ionic equation

A

HCO3- + H+ = H2O + CO2

44
Q

why is mols of soidum thiosulfate v low

A
  • so concentration of reactants doesnt fall significantly before end point reached
  • used up during initial rate period
45
Q

quenching with IODINE CLOCK method

A
  • take samples at various times
  • quench with ice
  • titrate using alkali
46
Q

why might u get anomalies where rate is too high

A
  • rate is too high
  • reaction exothermic
  • more collisions with E>= Ea
47
Q

what happens if no thiosulfate added in iodine clock

A

reaction goes blue black immediately

48
Q

purpose of thiosulfate

A
  • as soon as iodide reacts to form iodine, thio reacts to turns it back to iodide
  • to prevents colour change occuring until a set amuont of reaction occured
49
Q

how to use colorimetry for iodoine(3)

A
  • colorimetry
  • measure absorbance
  • CALIBRATION CURVE to turn it into concentration. absorbance proprotional to concentration
50
Q

biggest alkane hazard

A

TOXIC BY INHALATION

51
Q

reforming defition

A

converting straight chain HC to a ring/branched

52
Q

cracking defintion

A

breaking a longer HC to shorter chain HC

53
Q

describe waht happens to pi and sigma bonds in addition

A
  • pi bond breaks
  • sigma bond remains
  • as pi weaker
  • forms a carbocation intermediate
54
Q

alkene with acidificed potassium manganate (7)

A

DILUTE SULFURIC ACID
- forms a DIOL
- purple to colourless

55
Q

a fuel is …

A

a substance that produces energy

56
Q

why might the fuels be liquified

A

easier to transport

57
Q

hazard vs risk

A

hazard: potential to do harm
risk: likelihood harm will result

58
Q

which o the 2 ions has POLARIZING ability

A

cation

59
Q

formation of acid rain rain on limestone

A

REACTS with limestone to corrode buildings

60
Q

why conducgtivity different (ionic compounds)

A

cations are diff sizes

61
Q

why cant silicon conduct electricity

A
  • outer electorns FIXED in covalent bonds
  • no delocalised electrons
62
Q

why are polymers not sustainable

A

made from crude oil which is non-reneweable

63
Q

why is pi weaker than sigma

A
  • sigma direct end on overlap of orbitas- along line in between the 2 nuclei
  • pi = sideways overlap
64
Q

why is ice less dense than water

A
  • molecules spread out further apart
  • in a lattice
  • h bonds longer than covalent bonds
65
Q

why non polar insoluble n water

A

cant h bond with water

66
Q

ionic compounds solubility

A
  • soluble in water, ions hydrated
  • enthalpy change of hydration compensates for energy needed to break part lattice
  • INSOLUBE in non polar as any forces that would form between ion and substance weaker than ionic bondng
67
Q

describe the structure of. metal (3)

A
  • lattice
  • positive metal cations in layer
  • sea of delocalised electrons
68
Q

electrolyss of CuCrO4

A
  • ions migrate
  • Cu2+ blue colour towards cathode
  • CrO4 2- yellow colour towards anode
69
Q

2 sources of repulsion in ionic lattice

A
  • ions of same charge repel
  • positive nuclei repel
70
Q

purpose of reforming

A
  • more efficient combustion
  • fuels with a higher octane number
  • NO KNOCKING

chem (16 decks)

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